The widespread implementation of lightwave or optical transmission systems requires the use of connectors to couple and uncouple optical fibers for installation, testing and maintenance. In general, a practical connector must be capable of repeated couplings with a minimum of optical signal loss. Obviously, the connector should also be relatively inexpensive to manufacture.
Two types of optical fibers can be employed in optical transmission systems. Nonomode fibers transmit only one mode of light while multimode fibers allow multiple modes to propagate. Structurally, the diameter of the light transmitting core of a monomode fiber is 5-10 microns (.mu.m), or approximately one-fifth to one-tenth the core diameter of a multimode fiber. A low-loss optical connection typically requires the alignment of two fiber cores end-to-end. Monomode optical connectors, therefore, generally require considerably more precision than their multimode counterparts.
The molding of optical fiber connectors is one process being investigated for the fabrication of large numbers of economical, low loss connectors. One problem with molding a connector about an optical fiber is the bending of the fiber during molding. Such ending produces signal losses by allowing light to radiate out of the inner core of the fiber to its outer cladding. Severe bending can, of course, cause fiber breakage. Bending of the optical fiber also produces variations in the position of the optical fiber with respect to the mating end of the connector and the angle therebetween. These variations cause misalignment of the light transmitting fiber cores and thus signal losses when two connector halves are coupled together. While prior art techniques, such as that set forth in pending application Ser. No. 96,519, filed Nov. 21, 1979 and assigned to the present assignee, have addressed the problem of fiber bending, the tolerances on fiber location with respect to the mating end of the connector are not precise enough for use in the molding of low-loss monomode optical fiber connectors. This limitation is significant since monomode fibers transmit higher bit rate optical signals with less dispersion per unit distance than multimode fibers and are, therefore, extremely desirable for high-speed, long haul transmission systems.